1965 was the year America took the gloves off in Vietnam, moving from “advising and assisting” the South Vietnamese military to an active combat role. The first U.S. ground combat troops arrived there in March. That same month, the United States began bombing North Vietnam in Operation Rolling Thunder. In November, troops would take on North Vietnamese regulars for the first time in the Battle of Ia Drang Valley.

Once again, America was at war.

Among the casualties: President Lyndon B. Johnson’s legacy and Americans' faith in their government.

When Neil Armstrong took his small step for man in the lunar dust in July 1969, Americans saw it as proof there were no Earthly limits. Nothing then seemed beyond the reach of American power, prestige and know-how. It took Vietnam to expose the hubris in that sentiment.

The American Century was at its zenith. Unrivaled U.S. wealth and prosperity, predictable fruits of the postwar Pax Americana, lifted national influence to new heights globally. Hollywood, rock music, blue jeans and hamburgers carried American culture, taste and values to the far corners of the world.

Yet with the images of Apollo 11 still fresh on the mind, Vietnam forced Americans to accept limits to their power and to acknowledge their reach had exceeded their grasp.